Methods and apparatuses consistent with example embodiments relate to a communication device, and more particularly, to a delta modulator with a variable feedback gain, an analog-to-digital converter including the delta modulator, and a communication device including the delta modulator.
An analog-to-digital converter converts an analog input signal into a digital output signal. A wireless communication system uses an analog-to-digital converter to convert a received radio frequency (RF) signal into a baseband signal and generate a digital output signal based on an analog baseband signal. Examples of the analog-to-digital converter may include a flash-type analog-to-digital converter, a Successive Approximation Register (SAR)-type analog-to-digital converter, a sigma delta analog-to-digital converter, and the like, and each type may be used in a field according to the characteristics thereof. The flash-type analog-to-digital converter has fast operation speed, but includes 2n comparators to provide n-bit digital output signals. Thus, the flash-type analog-to-digital converter consumes a large amount of power and has a large implementation area. Compared with the flash-type analog-to-digital converter, the SAR-type analog-to-digital converter has low operation speed, but includes only one comparator. Thus, the SAR-type analog-to-digital converter consumes a small amount of power and has a small implementation area. The sigma delta analog-to-digital converter has a high signal-to-noise ratio (SNR), but a feedback gain of a delta modulator including passive elements is fixed to 1.